Dogs are generally considered to be in danger from heat when the ambient temperature rises above 85°F (29°C), and it becomes particularly risky above 90°F (32°C). At these temperatures, outdoor activities should be limited or avoided, and dogs must have constant access to water and shade to prevent heat stress or heatstroke

. Key temperature thresholds for dogs regarding heat:

• Below 75°F (24°C): Generally safe for most dogs, though caution is advised for brachycephalic breeds (e.g., Bulldogs, Pugs) which have difficulty breathing in heat

• 75–85°F (24–29°C): Use caution; avoid strenuous exercise during peak heat hours and provide plenty of water and shade

• Above 85°F (29°C): Significant risk; limit outdoor activities and ensure hydration and shade

• Above 90°F (32°C): Dangerous for most dogs; avoid outdoor activities and watch for signs of heat stress

Additionally, dogs' normal body temperature ranges from about 99.5°F to 102.5°F (37.5°C to 39.2°C). A body temperature above 103°F (39.5°C) is considered a fever, and temperatures above 106°F (41.1°C) can be fatal, often indicating heatstroke if caused by external heat

. Other considerations:

• Humidity greatly affects how dangerous heat is for dogs because it impairs their ability to cool down by panting. The heat index (temperature plus humidity) is a better measure of risk. If the sum of temperature (°F) and humidity (%) is 150 or higher, outdoor exercise should be avoided

• Asphalt and other surfaces can be much hotter than air temperature (up to 40°F hotter), which can burn dogs' paws at temperatures above 90°F

• Short walks (5 minutes or less) may be safe in moderate heat, but longer exposure should be avoided as dogs can overheat quickly

In summary, temperatures above 85°F start to become risky for dogs, and above 90°F is generally too hot for safe outdoor activity. Always provide shade, water, and monitor your dog closely for signs of heat stress in warm weather.